Iron deficiency is probably the most widespread nutritional problem in the industrial nations, yet there is a paucity of literature on the effects of iron deficiency on the aging progess. Since the population is continually exposed to chemicals in the environment and increasing quantities of therapeutic drugs are being consumed during the aging process, it is imperative that studies be conducted to determine the interrelationship of diet and the aging process on the drug metabolizing system. We plan to approach this problem by measuring the activities of specific enzymes associated with the mixed function oxidase system in the microsomes of the liver and kidneys of rats. Four experimental groups are proposed: 1. iron replete males, 2. iron-deficient males 3. iron-replete females, and 4. iron-deficient females. The enzyme activities to be monitored are: 1. cyctochrome P-450, 2. heme oxygenase, 3. p-chloro N-methylaniline N-demethylase, 4. aniline hydroxylase, 5. benzopyrene hydroxylase, and 6. microsomal NADPH. In addition, the effects of stannous chloride induction of heme oxygenase on the enzymes will be assayed. The enzyme levels or activities will be quantitated spectrophotometrically and spectrophotofluorometrically. The iron status of each animal will be determined by hemoglobin and hematocrit values as well as liver iron concentrations determined by atomic absorption spectrophotometry.